# Copyright 2013, Michael H. Goldwasser
#
# Developed for use with the book:
#
#    Data Structures and Algorithms in Python
#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
#    John Wiley & Sons, 2013
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from collections import MutableMapping


class MapBase(MutableMapping):
	"""Our own abstract base class that includes a nonpublic _Item class."""

	# ------------------------------- nested _Item class -------------------------------
	class _Item(object):
		"""Lightweight composite to store key-value pairs as map items."""
		__slots__ = '_key', '_value'

		def __init__(self, k, v):
			self._key = k
			self._value = v

		def __eq__(self, other):
			return self._key == other._key  # compare items based on their keys

		def __ne__(self, other):
			return not (self == other)  # opposite of __eq__

		def __lt__(self, other):
			return self._key < other._key  # compare items based on their keys
